深水钻井导管力学特性参数敏感性分析

Parametric Sensitivity Analysis of the Mechanical Behavior of Deepwater Drilling Conductor

深水钻井导管受力复杂,影响因素较多,主要包括平台偏移、海流流速、土壤强度、固井质量和低压井口出泥高度等,确定各影响因素的优先等级是深水钻井导管钻前设计和现场作业急需解决的问题。建立了深水钻井导管力学分析模型,分析了导管的力学特性,采用正交试验方法安排仿真试验方案,对仿真试验结果进行极差分析和方差分析,从而确定各影响因素对深水钻井导管力学特性的影响大小和显著性。研究结果表明,导管最大应力值出现在泥线以下8 m左右,影响导管最大Mises应力的因素依次为平台偏移、导管外径、导管壁厚、海流、低压井口出泥高度和固井质量等,其中平台偏移、导管几何参数和海流对最大Mises应力的影响高度显著,出泥高度和固井质量对导管最大Mises应力影响相对较小。通过分析发现,平台偏移和海流流速增大是造成导管载荷增加的根本原因,增大导管外径和壁厚可以有效减小导管应力。

The forces on the deepwater drilling conductor are complex and influenced by many factors, inclu- ding platform offset, ocean current velocity, clay strength, cementing quality and wellhead elevation above the mud-line. Determining the priority level of the factors is an issue that needs to be addressed urgently for pre-drilling design and field operation. A mechanics analysis model of deepwater drilling conductor is established, and the con- ductor mechanical behavior is analyzed based on the model. The simulation program is conducted based on orthogo- nal test method, and test results are analyzed through range analysis and variance analysis, thus, the impact and significance of each factor is determined. The study results show that the maximum stress of the conductor is about 8 m below the mud line. The factors that influence maximum Mises stress are, in order of significance, platform off- set, the outer diameter of the conductor, the wall thickness of conductor, ocean current, wellhead elevation a- bove the mud-line and cementing quality. The platform offset, the geometric parameter of the conductor and ocean current have highly significant impacts on maximum Mises stress, while the impacts of wellhead elevation above the mud-line and cementing quality on the maximum Mises stress is relatively small. The analysis revealed that the platform offset and ocean current velocity increment are the primary causes of conductor load increment, and increasing the diameter and wall thickness of conductor can effectively reduce the stress of the conductor.